2026 ICD-10-CM Diagnosis Code B25.0Cytomegaloviral pneumonitis
ICD-10-CM Codes›A00–B99›B25-B34›B25
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 6
- Not Chronic
B25.0 is a billable ICD-10-CM diagnosis code for cytomegaloviral pneumonitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 129 closely related codes. Coders also document this condition as cytomegaloviral pneumonia. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Pneumonia (except that caused by tuberculosis) and Viral infection.
For Medicare Advantage risk adjustment, B25.0 maps to CMS-HCC Category 6 (Opportunistic Infections) under the V28 model, adding a risk factor of about 0.381 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
B25.0 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Cytomegaloviral pneumonia
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Disease, diseased See Also: Syndrome;
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Cytomegalovirus Infections
Cytomegalovirus (CMV) is a virus found around the world. It is related to the viruses that cause chickenpox and infectious mononucleosis (mono). Between 50% and 80% of adults in the United States have had a CMV infection by age 40. Once CMV is in a person's body, it stays there for life.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert B25.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B25.0Overview
What is the ICD-10 code for cytomegaloviral pneumonitis?
The ICD-10-CM code for cytomegaloviral pneumonitis is B25.0 (sometimes written as B250). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is B25.0 (Cytomegaloviral disease) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report cytomegaloviral pneumonitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does B25.0 group to?
When cytomegaloviral pneumonitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, with relative weights from 0.7550 to 1.5627 depending on complications. Higher weights mean higher Medicare reimbursement.
Is B25.0 a CC or MCC?
CMS lists B25.0 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 129 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B25.0?
Under the General Equivalence Mappings, cytomegaloviral pneumonitis converts to ICD-9-CM 078.5 (cytomegaloviral disease) and 484.1 (pneum w cytomeg incl dis). The mapping is approximate, so confirm the match fits the documentation.
What HCC is B25.0?
B25.0 (cytomegaloviral pneumonitis) maps to CMS-HCC Category 6 (Opportunistic Infections), commonly written as HCC 6, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 6 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 5.
Does B25.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, B25.0 adds a risk adjustment factor of about 0.381 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.381 to 0.833 depending on the payment segment). HCC 6 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 6 category page.
